Wire wrapping?

jason_traud

I'm putting together a presentation that includes how the inner workings of a brushed, brushless, and stepper motor works. The YouTube channel The Engineering Mindset has some good graphics that I'd like to try to replicate like the attached image. The rest of the motor would be easy, but making the wire wrapping looks like it'll be difficult. 

I'm assuming that it's something like using the Helix tool to create a curve, create a plane on the end of that curve to set the cross section of the wire, then extrude down the path. However, the helix tool only accept cylinders. 

Would I need to essentially make a rounded rectangle shape, slice the curves created by using the helix tool on the fillets, then slice up the curves created on the corners and stich the four corners together?

 

S1mon

Making accurate coils would be pretty challenging. Making fake placeholders that are a bunch of loops would be much easier. I’m actually working on an electric motor at the moment, and the manufacturer doesn’t have the coils modeled. I might try to add a fake version to help understand weight and volume. If I do, I’ll post an image.

MichaelPascoe

This workflow would need some tweaking, but here's the general idea:

https://cad.onshape.com/documents/cd256fa63ba366c63ecb2f1a/w/6df15a4c285b4a0b7b94e014/e/70fdc0db76fc71bdeb9a443f?renderMode=0&uiState=6407601e147a9b3fb3e6a23f

eric_pesty

You could just do straight loops around as @S1mon suggests, or you could do a very close approximation fairly easily by making the "short ends" straight across, and angling the long side like this:


https://cad.onshape.com/documents/6024851754e8a4f2d31752fb/w/b81c38630d631ef3f0d1ecf1/e/f3bc4fca25323460155ee2eb

MichaelPascoe

That's pretty clean @eric_pesty. Nice approach!

eric_pesty

@MichaelPascoe
I like how you went all out with the lofted helixes!
I think using the wire diameter offset surface approach splitting your lofted helix would produce a really nice fitting coil.

StephenG

I am always fascinated by the extremes people go through to model an exact visual representation of the physical world. It is an easy trap to fall into but it is a real time waster with respect to getting things done. I have to admit I do it, but it is done as an intellectual challenge with the benefit being to expand my working knowledge of Onshape. For @jason_traud, the goal is to produce only a visual of a loop of wires around a crude visual for a motor stator; it is not something that is going to be manufactured.  

As @S1mon pointed out it makes a lot more sense (from a geometric engineering standpoint where fitment is a primary concern) to use a placeholder (simplified part geometry representing the volume of the wire bundle).

I constantly have to remind myself that my 3D model is nothing more than a 3D cartoon; it only needs to have enough geometric fidelity to support the concept I am trying to capture, communicate and support known downstream uses of the model. There is a very good reason why the recently added "External Threads" feature in Onshape does not produce (to the disappointed of many) geometric modeled threads. 

eric_pesty

@StephenG
Yes it's easy to get distracted and add unnecessary details...
Although it does depend on what the model ends up being used for. If purely for describing a design then "schematic" is the correct approach (so in this case you could just pattern some straight loops of wire or even not show anything provided you have done the "math" somewhere else to make sure the number of wraps ans wire size fits in the space! 
It gets a bit more muddy when you use the CAD models for illustration purpose such as manufacturing instructions or user documentation where more detail is required. We have actually crated "3D threads" (only on large diameter parts) to be able to show them in customer assembly instructions but we normally have a "high detail" configuration checkbox that is off by default when we do this.
We have also caught some potential issues before while creating "unnecessary" details before so it's not always completely wasted!

jason_traud

Yall rock! Thanks!

None of this needs to be functional. Just for visual representations when explaining the internals of a motor. I figure it'll make it easier to color code things for the slide deck. 

S1mon

Here's the reality of the motor that I'm dealing with:



There are plastic insulators around the stator (this is a motor for an electric scooter, so the rotor/stator situation is flipped from the typical situation), and the wire wrapping is very far from the perfection that you're likely to model in CAD. (Not to mention the cable tie and whatever that lump of white goop is - caulk? epoxy?)

It's possible that this is a hand-wound engineering sample, but I'm really not sure.

I will just be modeling a very simple shape which represents the bulk of each winding to show the max size for clearance.